EQ
Equalizers have specialized filters that influence the volume of specified frequencies or a range of frequencies within the audio spectrum. The audible frequency spectrum ranges from 20 Hz to 20 kHz. An equalizer can attenuate, boost, remove, or leave these frequencies unchanged. Changing the frequency of a sound or entire mix will alter its tone, volume, and harmonic make-up.
Types
Parametric EQ
Semi-Parametric
Parametric equalizers are the most common and versatile type of EQ used in music production. These multiband equalizers offer fully configurable and adjustable frequency bands. You can control the center frequency, level, and bandwidth of each frequency band with the highest precision.
parameters include: frequency, resonance/Q, gain, filter slope, filter high
A semi-parametric equalizer is a parametric equalizer without one or more features. Typically, the bandwidth Q has a fixed setting. You can only adjust the frequency and gain of each band. Many also don’t have an interactive display with an analyzer.
Dynamic EQ
Dynamic equalizers combine the precision of parametric equalization with the dynamic control of compression or expansion. This versatile combination gives you more control over shaping and enhancing sounds.
Graphical EQ
Dynamic equalizers are nonlinear processors. The filters react to either the internal audio source or are triggered by a sidechain input source. For example, cuts and boosts respond to the incoming audio that passes a set threshold level. This dynamic movement adapts to the music.
Graphic equalizers boost or attenuate a range of fixed frequencies using a bank of evenly spaced slider controls. They can also have up to 31 or more bands. More bands will provide higher accuracy over the frequency spectrum.
graphic equalizers with narrower bandwidths have greater precision. However, they’re not as effective for surgical work as a parametric EQ as there is no control over the filter shape and bandwidth of each band.
Shelving EQ
Shelving equalizers are the most basic type of EQ. A shelving equalizer boosts or attenuates frequencies above or below a specified cutoff point. Many shelving equalizers also have predetermined filter curves with a wide Q.
Filters
High shelf
Band pass
High cut/ low pass
Bell curve/ Peak filter
Low shelf
Notch filters
Low cut/ High pass
A low cut filter removes all frequencies below a specified frequency cutoff point. This filter is also known as a high pass filter because it passes all high frequencies above the cutoff point.
A low shelf filter attenuates or boosts frequencies below a specified frequency point. Low shelf filters don’t cut frequencies out completely like low cut filters. Instead, they gradually reduce or boost bass frequencies.
A high cut filter removes all frequencies above a specified frequency cutoff point. This filter is also known as a low pass filter because it passes all low frequencies below the cutoff point.
A high shelf filter attenuates or boosts frequencies above a specified frequency point. High shelf filters don’t cut frequencies out completely like high cut filters. Instead, they gradually reduce or boost treble frequencies.
A bell curve attenuates or boosts frequencies around a specified center frequency point. The bandwidth Q sets the width of the bell curve. Bell curve filters are also known as peak filters.
A band pass filter passes a range of frequencies around a specified center frequency point. Low and high frequencies outside the range are attenuated.
notch filter attenuates a range of frequencies around a specified center frequency point. Low and high frequencies pass on either side of the frequency range. Notch filters are also known as band stop filters.